Typescript issue: Type is not assignable to type 'Encrypter'.

[NayamAmarshe]

I have this snippet:

// LOCALSTORAGE-SLIM
ls.config.encrypter = (data: unknown, secret: string): string => {
  return CryptoJS.AES.encrypt(data, secret).toString();
};
ls.config.decrypter = (encryptedString, secret) => {
  const bytes = CryptoJS.AES.decrypt(encryptedString, secret);
  return bytes.toString(CryptoJS.enc.Utf8);
};

but typescript throws an error: Type '(data: unknown, secret: string) => string' is not assignable to type 'Encrypter'.

How can I fix this? Tried a few things but they don't seem to work.

[niketpathak]

Hello @NayamAmarshe ,

You need to use type-assertion since localstorage-slim does not have an idea about what you plan to use internally within the Encrypter/Decrypter functions (i.e. CryptoJS or some other encryption library)

If you try this, your compiler will not complain ->

ls.config.encrypter = (data, secret): string => {
  return CryptoJS.AES.encrypt((data as string).toString(), secret as string).toString();
};
ls.config.decrypter = (encryptedString, secret) => {
  const bytes = CryptoJS.AES.decrypt(encryptedString as string, secret as string);
  return bytes.toString(CryptoJS.enc.Utf8);
};

Here is a simple article on type-assertion to clarify your doubts.

[NayamAmarshe]

Thanks a lot Niket!
I tried this and it fixed the issue:

ls.config.encrypter = (data, secret) => {
  return CryptoJS.AES.encrypt(
    JSON.stringify(data),
    secret as string
  ).toString();
};

ls.config.decrypter = (data, secret) => {
  try {
    return JSON.parse(
      CryptoJS.AES.decrypt(data as any, secret as any).toString(
        CryptoJS.enc.Utf8
      )
    );
  } catch (e) {
    console.log(e);
    return data;
  }
};

[niketpathak]

While your solution will work, its always better to use specific types rather using any since that kinda beats the purpose of using typescript.